The experiments described in this proposal are designed to evaluate an hypothesis of the functional organization of some brain systems involved in reward and mood. This hypothesis may be of value in understanding the neuroanatomical and neurochemical bases of different components of affective disorders (depression and mania) in humans. The hypothesis proposes that dopaminergic (DA) neurotransmission in nucleus accumbens and ventral anterior striatum biases the decision process by which the amount of effort perceived necessary to attain a goal is weighed against the value of the goal. Catecholaminergic transmission elsewhere in brain is proposed to bias the value of the goal. Alterations in these two processes: (a) willingness to exert effort, and (b) evaluation of reward/pleasure are often considered to be among the primary components of emotional depression in humans. It is hoped that these experiments with rats will provide information concerning the neuroanatomical and neurochemical bases of these two components. The experiments will examine the effects of intracerebral microinjections of drugs which alter DA and other transmission on single-lever and autotitration intracranial self-stimulation. The results will be interpreted by means of an analytical scheme which allows separation of changes in effort from changes in reward evaluation.